Regurgitation and reingestion (R/R) behavior is common in all species of captive great apes, yet has not been observed in wild populations. This disparity in behavior may be indicative of suboptimal welfare in the captive population. In this study we investigated R/R behavior in six Western lowland gorillas (Gorilla gorilla) and six orangutans (Pongo pygmaeus), housed at the Smithsonian’s National Zoo, under multiple feeding conditions. It was our aim to identify food items that were most associated with R/R and to modify ape diets accordingly by reducing or eliminating these items. Twelve hours of observational data were collected for each subject, at each feeding, under each condition for a total of 1,512 hours. Observation sessions were 90 minutes in duration and coincided with the beginning of each feeding. All instances of R/R were recorded, as well as meal duration, latency to regurgitation and overall activity levels. Consistent with previous studies, we found that primate chow and fruit had a greater effect on R/R frequency than did vegetables and greens. In addition, we found a negative correlation between activity level and R/R (rs=-0.48, p<0.001) in the gorilla group. These findings suggest that the prevalence of R/R in captive apes is related not only to a diet that is higher in starch and sugar, but also to their diminished activity rate when compared to their wild counterparts.